Current methods of mechanized recording have a significant deficiency, so basic that it is rarely if ever considered: In order to record any event, a human user must decide to record it prior to the event taking place. Thus, with the exception of continuous monitoring systems (discussed below), recording is generally limited to explicit dictation of words or staging of events.
Accordingly, there is a need for a recording method that effectively allows a user to decide to record an event after the event has taken place. One way to achieve this is by continuously recording all ambient events in a continuous logical loop on a finite extent of recording medium, allowing users to select for permanent preservation portions of the material thus recorded, before they are overwritten with new material. Although this method has not heretofore been devised, prior art for some of its components does exist in a number of forms:
(1) Tape formats, including cartridges and cassettes, that record on a continuous loop of recording medium. These have been used only to record a single sequence of material, not extending beyond the length of the medium itself. The loop format serves merely to eliminate the need for rewinding the tape when repeatedly playing it. PA0 (2) Devices such as the flight data recorder or "black box" used in aviation. This type of device does record events in a continuous loop, overwriting the material earliest recorded with fresh material so that, by recording continuously, the medium always contains the most recently recorded material. However, the data stored in these devices are inspected only on special occasions (such as a crash), and no means of selecting material for permanent preservation is provided. PA0 (3) Systems used for telephone monitoring which produce a continuous record. These generally record automatically, and only when a telephone is in use. Some of these allow recall of the most recent data recorded. Further, some of these systems use continuous-loop buffers so that mechanized processes may determine the suitability of recorded material for permanent storage. These systems preserve the entire record of continuously recorded material (subject only to mechanized determination of suitability), thereby requiring an indeterminate supply of recording medium. PA0 (4) Recording systems that detect intervals of silence during recording and thereby conserve recording medium.
The foregoing prior art is substantially in the public domain. Various digital voice-message dictation, storage and editing systems are in the patent literature:
U.S. Pat. No. 4,627,001 (Stapleford et al., 1986) discloses a "dictation and editing system including microphone and keyboard inputs to a programmed computer system." This invention provides a visual display which shows a series of "voice token marks," representing speech or sound recorded by the microphone, interspersed with characters entered via the keyboard. Thus it enables a user to mark or annotate points in his or her voice dictation. The same basic ideas are amplified in the same inventors' U.S. Pat. No. 4,779,209 (1988).
U.S. Pat. No. 5,265,075 (Bergeron et al., 1993) discloses a "voice processing system with editable voice files," including a "central dictation system for prerecording standard voice files," and enabling users to make copies of and edit these prerecorded files.
U.S. Pat. No. 5,008,835 (Jachmann et al., 1991) discloses a voice mail system which enables users to interrupt playback of voice mail messages to record replies.
U.S. Pat. No. 4,375,083 (Maxemchuk, 1983) discloses a method for editing previously recorded voice messages, which detects intervals of silence, separates the recording into segments at these intervals, and enables users to edit the recording by rearranging and/or deleting these segments.
By their own language, all of these inventions have to do explicitly with dictation, that is, with recording of speech or events as a result of a prior decision to record. Moreover, these systems all share significant drawbacks with recording methods in the public domain, such as preserving essentially the entire record of recorded material when operated continuously, thereby requiring an indeterminate supply of recording medium and requiring users to edit out any unwanted portions.
The patent literature also discloses a number of recording methods and apparati which record onto a circular buffer, recording new material in place of the oldest recorded material so that the buffer always contains the most recently recorded material.
U.S. Pat. No. 5,371,551 (Logan and Goessling, 1994) discloses a "time-delayed video system using concurrent recording and playback" which digitizes and stores continuously acquired video or audio signals in a circular buffer, writing over the earliest recorded material when the buffer is full. This patent fails to disclose, teach or otherwise suggest selection or recorded material for permanent storage or indeed any permanent storage of recorded material.
U.S. Pat. No. 5,465,120 (Schultheiss, 1995) discloses a "spiral buffer for video editing" which digitizes and stores an input video signal as it is simultaneously being catalogued by an operator. Storage is provided in a circular buffer of random-access memory, in which recorded material may be overwritten with newly received material as long as the original material was not marked by the cataloging process to be kept. Although this invention provides for the selection of recorded material for permanent retention in the form of its "cataloging and capturing" step, this action is performed simultaneously with receipt of the original signal. No such selection of recorded material can be made subsequent to its original receipt as the present invention allows) unless, of course, one originally captured it as it was received.
U.S. Pat. Nos. 5,487,754, 5,487,755, and 5,431,691 (Snell et al, 1995-1996) disclose a method of continuously recording a sequence of cardiac pacing events and their respective rates of occurrence in an event record stored on a circular buffer connected to a pacemaker implanted in a patient's body, and providing means for retrieving data from this event record via a telemetry link with a programming device located in a physician's office. Provision is made for displaying statistical views of the stored data and for storing the event record in case of a critical event such as the patient experiencing palpitations; however, there is no suggestion of reproducing the stored data except in such statistical views, or of selecting any part or parts of the event record for permanent storage, either inside or outside the circular buffer.
None of the foregoing inventions involving circular-buffer recording discloses, teaches or otherwise suggests providing for the recording, storage or reproduction of "live," external events, as the present invention does. Logan is designed to receive broadcast programming on a predetermined broadcast channel while it is operating (it may be preprogrammed by means of a clock in the manner of current videocassette recorders). Schultheiss is designed for editing already-recorded video. Snell is designed for the statistical sampling of, and the statistical display of, discrete cardiac pacing events, a wholly different application from the present invention.
In conclusion, with respect to all of the prior art, the present invention has the advantage of enabling users to decide to record events on a finite supply of recording medium after those events have occurred, and the further advantage of reducing or eliminating the need to review continuously recorded material and discard any unwanted portions thereof.